As parallel data buses have started to become less popular, they are being replaced by high speed serial communication buses. The electronics industry has used eye diagrams for several years as a way to specify the quality of a serial digital signal. The serial digital signal is an analog signal that transitions between two voltage levels representing, respectively, a logic “1” and a logic “0”, the transitions occurring at regular clock intervals. A mask or keep-out region is used to define an area which should not be traversed by the digital signals during a unit interval (UI) or symbol period, corresponding to one clock interval, in order to ensure the highest quality data recovery. Oscilloscopes are very useful tools for displaying eye diagrams and showing eye violations, as shown in prior art FIG. 1.
Unfortunately, the usefulness of an eye diagram in current oscilloscopes is limited by the fact that an eye diagram is a post-processing tool, meaning that the data record must have already been captured, in response to the detection of a unique trigger condition, before the data waveform can be applied to a mask to determine the occurrence of a mask violation.
That is, oscilloscope users who are debugging serial digital data channels must capture a record of data by employing one of numerous known triggers and use a software-based post-processing search of the acquired data record to find eye violations. This technique suffers from a relatively long “dead time” between acquisitions during which the oscilloscope is processing the most recently acquired data record. Moreover, it may be that the acquired data record that is currently being processed does not include any eye violations, resulting in a waste of processing time in which the oscilloscope is engaged in a futile search for non-existent anomalies. Unfortunately, data that does include eye violations will be overlooked if that data occurs when the oscilloscope is busy searching the current record.
What is needed is an apparatus and method that avoids such futile searches for non-existent eye violations, thereby substantially eliminating the dead time related to such futile searches.